1. Field of the Invention
The present invention relates to an ink jet apparatus capable of forming a high density recording image, and to a conductive ink mixture effective to be used for the ink jet apparatus.
2. Description of the Related Art
Conventionally, there have been known ink jet apparatuses with a bubble jet system and a current-carrying jet system. The bubble jet system is operated by vaporizing ink in a vessel using heat generated by a heat-generating resistor for generating bubbles of ink, and discharging the ink increased in pressure from a nozzle of the vessel. On the other hand, the current-carrying jet system is operated by heating conductive ink by applying a current thereto, vaporizing ink by the heat thus generated for generating bubbles of ink, and discharging the ink increased in pressure from a nozzle of a vessel.
In the bubble jet system, ink contacted with the heat-generating surface of the heat-generating resistor is vaporized by heating. Specifically, in this system, since the heat is imparted to ink from the heat-generating surface of the heat-generating resistor, an energy imparted to ink is limited by the area of the heat-generating surface of the heat-generating resistor, with a result that a discharge energy to be applied to ink is limited. Even when a large amount of current is allowed to flow to the heat-generating resistor for heating ink to the extent over the above limitation, the discharge energy to be applied to ink is not increased and the heat-generating resistor tends to be broken.
On the other hand, in the current-carrying jet system, since conductive ink applied with a current has a homogeneous composition and thereby it has a constant resistance, there is no means for increasing an energy imparted to ink and enlarging the discharge force to be applied to ink.
Recently, in the ink jet apparatus, it has been required to enhance the density of a dot to be printed for improving the fineness of the printing. To meet this requirement, the opening diameter and the arrangement pitch of each nozzle for discharging ink must be smaller than conventional values. In the prior art ink jet apparatus, however, the discharge force to be applied to ink cannot be easily increased, and when the opening diameter and the arrangement pitch of each nozzle are made smaller while the discharge force to be applied to ink is kept as being conventional, ink sediment and refuse tend to be collected in the nozzle, to thus clog it. In this way, the prior art ink jet apparatus has a limitation in the discharge force to be applied to ink, and consequently, it presents a problem having a difficulty in improving the fineness of printing.